Necrotizing enterocolitis (NEC) is a severe, sometimes life-threatening inflammation of the intestine that occurs most often in premature babies. If it progresses, the wall of the intestine may perforate, spilling bacteria and stool into the abdomen. Parts or all of the intestine may die. Despite 30 years of clinical studies, the cause of NEC remains unknown.

In this study, we will be conducting an independent case-control validation study to verify the diagnostic and prognostic biomarker panels, develop validated biomarkers on boisensors in preparation for prospective validation studies, and conduct independent prospective validation of biosensor based biomarker panels on clinical samples.

Inclusion Criteria - NEC/Sepsis Cohort GA < 29 weeks Current age equal or <12 weeks Suspicion of NEC or Sepsis

Exclusion - NEC/Sepsis Cohort Current or prior diagnosis of NEC Early onset infection (equal or <72 hours of life) Previous diagnosis of sepsis within 7 days Previous abdominal surgery Significant congenital anomaly

Inclusion Criteria - SIP Cohort Infants born at <29 weeks gestation Equal to or <12 weeks of age at the time of eligibility assessment a decision to perform surgery (or drain) for suspected NEC or SIP

Exclusion - SIP Cohort Congenital infection (Equal to <72 hours of life) Prior episode of NEC or SIP Prior laparotomy or drain for SIP or NEC

Prematurely-born infants with with suspected necrotizing enterocolitis, sepsis or SIP who meet study entry criteria